1. Field of the Invention
This invention relates to the preparation of hydroxyanthraquinones and, more particularly, to the preparation of 1-hydroxyanthraquinone and dihydroxyanthraquinones from the corresponding nitroanthraquinones.
2. Description of the Prior Art
Hydroxyanthraquinones, and, particularly, hydroxyanthraquinones substituted in 1 or 2 peri positions with hydroxy groups such as 1-hydroxyanthraquinone; 1,5-dihydroxyanthraquinone; and 1,8-dihydroxyanthraquinone are valuable intermediates for dye manufacture. These compounds also have utility as starting materials for other useful and desirable dye intermediates and in the pharmaceutical area.
Various methods for preparing these hydroxyanthraquinones are described in the prior art. The disclosed preparative routes to 1-hydroxyanthraquinone include high temperature (190.degree. to 200.degree. C.) hydrolysis of 1-nitroanthraquinone in water containing calcium hydroxide or pyridine; high temperature aqueous hydrolysis of 1-anthraquinonesulfonic acid with alkali and decomposition of diazotized 1-aminoanthraquinone. More recent methods include the aqueous hydrolysis of 1-anthraquinonesulfonic acid at 200.degree.-300.degree. C. (USSR Pat. No. 68330) and the oxidation of either anthracene or anthraquinone in an aqueous system with air and bromide at about 260.degree. C. at 75 atmospheres pressure (German Pat. No. 1,160,124).
The preparative routes to 1,5-dihydroxyanthraquinone and 1,8-dihydroxyanthraquinone are analogous to those for 1-hydroxyanthraquinone. Published references disclose the alkaline hydrolysis of 1,5-dinitroanthraquinone and 1,8-dinitroanthraquinone at 200.degree. C., the caustic fusion of 1,5-anthraquinonedisulfonic acid and 1,8-anthraquinonedisulfonic acid and the diazotization of 1,5-diaminoanthraquinone and 1,8-diaminoanthraquinone followed by decomposition of the bisdiazo compound.
More recently, USSR Pat. No. 230,187 describes the caustic fusion of the sodium salts of 1,5-anthraquinonedisulfonic acid and 1,8-anthraquinonedisulfonic acid at a temperature of 140.degree.-160.degree. C. and a pressure of about 3 to 4 atmospheres. German Pat. No. 2,108,575 discloses the condensation of m-hydroxybenzoic acid in a sodium chloride-aluminum chloride melt at 170.degree. to 210.degree. C. to give good yields of 1,5-dihydroxyanthraquinone. U.S. Pat. No. 3,884,943 discloses the acid hydrolysis of 1,5-dimethoxyanthraquinone and 1,8-dimethoxyanthraquinone in glacial acetic acid-sulfuric acid to the corresponding dihydroxyanthraquinones, the dihydroxyanthraquinones being separated by fractional crystallization from the hydrolysis medium. U.S. Pat. No. 4,002,654 describes the alkaline hydrolysis of 1,5-anthraquinonedisulfonic acid and 1,8-anthraquinonedisulfonic acid at 300.degree.-340.degree. C. using calcium oxide.
The previously known methods for preparing hydroxyanthraquinones, however, have various drawbacks. For example, the methods most often used in the past are those based on anthraquinonesulfonic acids in which the sulfo groups are in one or more peri positions which can only be made by the sulfonation of anthraquinone in the presence of mercury or its salts. These methods are ecologically unacceptable in view of the subsequent discharge of mercury compounds to the environment. Attempts to isolate these compounds and/or remove them from effluent streams have been either ineffective or are economically unattractive.
The methods for preparing hydroxyanthraquinones starting with peri nitrated anthraquinones require large amounts of energy to achieve the necessary high temperatures and require specially designed pressure or fusion vessels to withstand the rigorous conditions employed.
Moreover, the known methods for preparing the hydroxyanthraquinones generally require multi-step procedures.
It is an object of the present invention, therefore, to provide a process for the preparation of hydroxyanthraquinones and, particularly, anthraquinone substituted with hydroxy groups in one or two peri positions and which is devoid of the disadvantages of the prior art methods.
This and other objects will be apparent to those skilled in the art from the following description and discussion.